1. Field of the Invention
This invention relates to an infrared detector, and more particularly to an IR (infrared) detector which enables both detection of a moving person and detection of radiation temperature by using a single pyroelectric infrared detector element.
2. Description of the Prior Art
A pyroelectric infrared detector element is a thermal type of infrared detector element having the differential type of output characteristics, which has been used for various applications because of its features such as high sensitivity, availability under room temperature, and low cost. The representative applications include a detector for moving person and a detector for radiation temperature of a disaster preventing equipment and other industrial equipment.
FIG. 5 shows an example of conventional moving person detector.
This moving person detector 201 comprises a pyroelectric infrared detector element 1, an AC amplifier 30 which amplifies output from the pyroelectric infrared detector element 1 in AC mode, and a comparator 71 which compares output from the AC amplifier 30 to the prespecified reference value, and outputs a moving person detection signal when a person comes into a field of view of the pyroelectric infrared detector element 1.
In the moving person detector 201, the target for detection is only a change caused by movement of a person within the total infrared ray energy input to the pyroelectric infrared detector element 1. This change level is very weak, and accordingly a gain (amplification factor) of the AC amplifier 30 is required around 70 dB.
FIG. 6 shows an example of conventional radiation temperature detector.
This radiation temperature detector 202 comprises the pyroelectric infrared detector element 1, a chopper mechanism 2 for cyclically interrupting the infrared ray input to the pyroelectric infrared detector element 1, a chopper driving circuit 21 drives the chopper mechanism 2, an AC amplifier 40 which amplifies output from the pyroelectric infrared detector element 1 in AC mode, a sample/hold circuit 41 for synchronous detecting an output signal from the AC amplifier 40, a sampling signal generating circuit 42 which generates a sampling signal synchronized to the output signal from the chopper driving circuit 21 and gives the sampling signal to the sample/hold circuit 41, a temperature compensator 51 which generates a temperature compensating signal based on the temperature information detected by a temperature detecting element (not shown) provided adjacent to the chopper mechanism 2, and a DC amplifier 61 which generates a radiation temperature detection signal which is proportional to the infrared ray energy input to the pyroelectric infrared detector element 1; and outputs a radiation temperature detection signal which is proportional to intensity of the infrared ray energy radiated from an object within a field of view of the pyroelectric infrared detector element 1, namely radiation temperature of the object.
In a radiation temperature detector 202, the target for detection is the total infrared ray energy input to the pyroelectric infrared detector element 1. This is enabled by cyclically interrupting the infrared ray energy input to the pyroelectric infrared detector element 1 with the chopper mechanism 2. A level of this total infrared ray energy is relatively high, and the gain of the AC amplifier 40 is in a range from 30 to 40 dB.
In recent years, functions of electric houseware have been becoming more and more sophisticated because of introduction of microcomputers, and now incorporation of a detector for collecting various types of control information is required.
For instance, in air conditioners for home use, incorporation of a detector for moving person to collect information on movement of human bodies or a radiation temperature detector to collect information on temperature of a floor surface or a wall surface in a room is required.
However, if both the moving person detector 201 and the radiation temperature detector 202 are to be incorporated in one equipment, the configuration would become too complicated with the size becoming too large, and also the price would become too expensive.